Engine Random Misfire

[ErraticGalaxy]

Okay so I've gone all over the Internet trying to figure out what the hell this problem I'm having with my car is and can't figure it out. Took it to the shop and they couldn't even figure it out. So now my only option is to go online and try to hope someone else has had this problem but hasn't posted anything about it.

As you can read the title I'm having a misfire. It started happening about 1 or 2 months ago. Didn't think that bad of it because it was that big of a problem. Then it got worse.. I changed out the spark plugs my self, changed out the coil pack. Had the wiring checked and it turned out okay. Replaced a fuel injector.. NOTHING. And also changed out a camshaft position sensor. Same problem and it seems like it gets worse over time. It happens totally RANDOM. When in idle, accelerating, but usually stops when I'm on the highway.

The vehicle is a 2005 Mustang GT 3V with 199,000 miles. Yes it's a lot but it's been maintained very well and this is the first MAJOR problem I've had with it. I'm running out of options.

It also saying ONLY Cylinder 5.. So it's not a global problem. Only Cylinder 5, or at least that's what I think.

 

[MustangIIMatt]

Misleading thread title is misleading (random misfire and a cylinder 5 misfire are two different things).

But I digress...


Misfires are easy to diagnose when isolated to one cylinder.

First things first, verify the source of the misfire.

Swap the spark plug from cylinder 5 with one from another cylinder and the coil from 5 with the coil from another (different) cylinder (example would be to use 6 for the plug and 7 for the coil). Start the car and run the codes. If the misfire moved from 5 to one of the other cylinders, the part you moved to that cylinder is bad. If the misfire doesn't move, keep reading.

Make sure you are getting fuel to cylinder 5. A set of noid lights (parts stores have them either in their loaner tools or for sale) will tell you if the injector is getting signal to squirt fuel or not, if it is, swap the injector with one from another cylinder (do while engine is cool and after relieving fuel pressure) and starting the engine and running codes to see if the misfire moves. If it does, you need an injector. If you weren't getting signal to the injector, the problem is in the wiring harness or ECM. If the wiring and injector check out, keep reading.

If you have spark and fuel, the problem is mechanical. Buy/rent/borrow a compression tester and do a compression test. There are videos on Youtube on how to do one, and most testers come with basic instructions. If cylinder 5 is in spec and within tolerances in relation to the other 7 cylinders, the problem is in the valvetrain. If it's very low or zero, the problem is going to require some or more engine teardown to find. Either way, at that point, you're pulling a valvecover.

 

[ErraticGalaxy]

I'm sorry about the title, I was meaning random because the misfire does happen at random times.

But I've done a compression test and it came back looking fine. Coils were switched, spark plugs as well. Everything that you stated came back looking okay. I'm getting fuel to every injector but yet still misfiring. So basically from here what you're telling me is that the problem is in the valve train? Possibly a stuck lifter?

 

[ErraticGalaxy]

I'm sorry about the title, I was meaning random because the misfire does happen at random times.

But I've done a compression test and it came back looking fine. Coils were switched, spark plugs as well. Everything that you stated came back looking okay. I'm getting fuel to every injector but yet still misfiring. So basically from here what you're telling me is that the problem is in the valve train? Possibly a stuck lifter or something?

 

[ErraticGalaxy]

I'm sorry about the title, I was meaning random because the misfire does happen at random times.

But I've done a compression test and it came back looking fine. Coils were switched, spark plugs as well. Everything that you stated came back looking okay. I'm getting fuel to every injector but yet still misfiring. So basically from here what you're telling me is that the problem is in the valve train? Possibly a stuck lifter or something?

 

[RaggedGT]

Triple post ftw lol
Can you hear the timing chains making any noise?

 

[ErraticGalaxy]

Triple post ftw lol
Can you hear the timing chains making any noise?

Lol it kept giving me an error so I kept trying to post.
I do hear a noise but I'm sure it's not the timing chain. It's a ticking noise.

 

[RaggedGT]

Recently I had an F150 with the 3V, and it had misfire codes with new coils/plugs/injectors-other shop diagnosed. It was ticking as well. Pulled the timing cover and the chain on the passenger side had a lot of slop in it. Put a timing chain kit in it and cleared it right up. Not saying it's your issue,but the closest thing that I can relate lol
@74stang2togo will be back through eventually,he's pretty good at these internet diagnostics

 

[Noobz347]

Hey guys... leave those posts there so I can show it to @MRaburn

 

[MustangIIMatt]

I'm sorry about the title, I was meaning random because the misfire does happen at random times.

But I've done a compression test and it came back looking fine. Coils were switched, spark plugs as well. Everything that you stated came back looking okay. I'm getting fuel to every injector but yet still misfiring. So basically from here what you're telling me is that the problem is in the valve train? Possibly a stuck lifter or something?

Wiped cam lobe, broken valvespring, bent valve, stuck valve, lifter/tappet issues, are all possibilities. Timing chain issues aren't outside of the realm of possibility either, they are what drives the cams, and in turn, move the rest of the valvetrain components. I'd pull the valvecover on that bank and take a look. @RaggedGT will put up the Matt-signal anywhere he thinks I'm needed. He's the Commissioner Gordon to my Batman.

 

[ErraticGalaxy]

Gonna check that out on an off day, will come back Monday with results and pics hopefully.

 

[racerraj]

A roller rocker on my 06 froze a couple weeks ago on mine. It ate the cam lobe, then ejected and knocked the valve stem retainer off. That dropped a valve. Head is rebuilt and back on, still have a little reassembly to do before I fire it back up. Don't drive it until you fix it. Mine was a light tick, I was hoping it would make it to the weekend when I could check it. I probably would not have had to pull the head, but I am sure I still would have needed a cam, lifters, and rockers. I hope you catch yours before it takes too many parts out.

 

[ErraticGalaxy]

Okay I'm back, honestly I'm thinking that my problem is just the fuel injectors. I got a code today saying how the injector (Cylinder 2 now) was open and didn't want to close which means it was just dumping fuel into the cylinder. My check engine light was also flashing and I looked that up and it said this..

"If the light is blinking, engine misfire is occurring which could
damage your catalytic converter. Drive in a moderate fashion (avoid
heavy acceleration and deceleration) and have your vehicle serviced
immediately by your authorized dealer."

Which makes sense because I do hear my car backfiring. So I unplugged the injector for cylinder 2 and drove back home. No other misfire was happening except for that one. I'm guessing the injectors were just all going out at the same time.. Which means.. Replace all injectors, THEN take apart the engine and actually look into the ticking it's making.